Applications of magnetic liquid technology to damping phenomenon are reviewed. Products utilizing ferrofluids, such as a rotary viscous inertia damper, linear damper, damper/seal assembly, and dashpot are discussed. The rotary dampers are used to enhance stepper motor performance. A magnetic liquid film sheared between a moving and stationary component forms the basis of these devices. The fluid is retained by magnetic forces and does not leak out. Examples of actual use of these dampers on operating systems, along with the test results, are presented.

A review of damping applications of ferrofluids

Ferrofluids have novel properties and their behaviour in magnetic fields leads to many interesting applications. Although magnetic fluids are already used in some devices they have not yet been exploited to any extent

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Technological applications of ferrofluids

Two stage magnetic fluid vacuum seal for variable radial clearance

Numerical analysis on the action of centrifuge force in magnetic fluid rotating shaft seals

Ferrofluid rotary seal with replenishment system for sealing liquids

Three magnetic fluid seals custom engineered to meet specific application objectives are discussed. These seals are: a belt edge seal, a large diameter seal and a centrifugal seal. Extensive experimental data were acquired on the first two seals to determine their performance characteristics. Some of these test results are compared with the theoretical expectations. Numerical computations are made on the centrifugal seal to Predict its sealing capabilites. Presented at the 34th Annual Meeting in St. Louis, Missouri, April 30-May 3, 1979

Magnetic Fluid Seals for Special Applications

In this paper recent work in design and testing of two special magnetic liquid seals extending the state-of-the-art of ferrofluidic sealing is discussed. These custom seals are a moving belt edge seal and an exclusion seal. The first seal provides a hermetic barrier to solid particulates expected to be present in enclosed nuclear environments. The second seal is used on a magnetic disk drive spindle and reduces the particulate contaminants in the memory disk pack area by up to three orders of magnitude. In addition, bearing life in the spindle is found to be doubled due to reduction of operating temperature. The fundamentals of magnetic fluid sealing are presented in terms of magnetic circuit design and physical properties of ferrofluids.

P. Stahl

Papers

Magnetic Fluid Seals for Special Applications

Recent advances in magnetic liquid sealing